In Madison, Wis., water is part of the culture. The city is home to Lake Monona and Lake Mendota, which act as an aquatic back yard for tourists, anglers and the city’s nearly 250,000 residents. When the Madison Metropolitan Sewerage District decided to invest in phosphorus-reducing technology, protecting that water was part of the decision.

But in addition to safeguarding local waters, MMSD also wanted to improve plant process. Although MMSD’s effluent contains comparably low phosphorus and is discharged downstream from the city’s chain of lakes, the district has been coping for years with digester foaming issues and hard struvite buildup in wastewater treatment plant pipes .

Accordingly, it became evident a regional utility known for blazing trails needed to make another move. 

The road to resource recovery
In 2008, the district began a partnership with Ostara Nutrient Recovery Technologies to install a harvesting system that extracts phosphorus from wastewater sludge and converts it into Crystal Green, an eco-friendly fertilizer that can be marketed and sold to the general public.

“The Ostara process is reducing phosphorus in our biosolids that we apply to our Metrogrow program,” says Chief Engineer and Plant Director Michael Mucha. “A reduction of phosphorus by about one third in our biosolids protects the quality of lakes and streams in the Madison area.”

It took time to put the nutrient-harvesting project together.

“We requested proposals from a variety of nutrient recovery processes and evaluated them based on their science and ability to deliver on the results they promised,” says Mucha. “We visited Ostara’s showcase facility in Vancouver and concluded the system worked best with our treatment process here at the plant.”

Finally, at the end of 2013, MMSD completed system upgrades at the Nine Springs WWTP, which included enhancements to the plant’s digestion process and the Ostara nutrient-harvesting technology, making Madison the first municipality in Wisconsin to use the system.

Reaping the benefits
The environmental benefits of the phosphorus-harvesting program are clear, and the economics are advantageous. The district hopes to receive $250,000 in annual revenue from Crystal Green sales, which would benefit district customers and help pay for future plant upgrades.

“With most wastewater treatment plants, the predominant revenue source is service charges to our customers, and that will always be the case, but if we can look for other sources and are able to market the resources we harvest, that will help us move toward defraying the cost to our citizens,” says Mucha.

By reducing struvite buildup in pipes and limiting digester foaming, the process will also reduce maintenance costs.

Ostara will handle fertilizer marketing and distribution efforts.

“We produce the product for them, so we’re essentially a wholesale operation,” he says.

The harvesting system cost roughly $3 million and was part of a larger $40 million plant upgrade project. The district relied on a low-interest loan from Wisconsin Clean Water Fund to finance the project.

A community affair
Although Crystal Green won’t be sold in the Madison area, district officials are satisfied with its economic value and how well the construction process and early-stage day-to-day workings have gone .

“With innovative new technologies you have to expect that it takes time to break the process in. We’re dialing it in right now,” says Mucha. “I think this new technology has gone very smoothly. We’ve been able to complete this project on time, on budget, and we’re producing a product, so I feel very good about [its] success.

“The Madison community has been very supportive of this facility as a visible operation and a valuable resource to the community for being able to provide products that are valuable to people, and for effective use of our ratepayers’ money,” he says.

Not only that, but Mucha sees the upgrade as an opportunity to shift the course of the wastewater industry.

“I think the district feels that if we can push the wastewater industry into even more resource recovery — even more programs that benefit public health and the environment — we’ll continue to feel a sense of responsibility and commitment to making that happen,” Mucha concludes.